Paul Anka spills he wrote MJ's new song nearly twenty years ago -- and another artist sang it

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Michael Jackson's newest single, billed as the singer's latest recording, was actually written for Jackson nearly two decades ago -- and was released without giving credit to Jackson's co-writer Paul Anka, Anka and Jackson's estate confirmed Monday.

Michael Jackson's newest single, billed as the singer's latest recording, was actually written for Jackson nearly two decades ago -- and was released without giving credit to Jackson's co-writer Paul Anka, Anka and Jackson's estate confirmed Monday.

Anka, the hitmaker behind "Diana" and Frank Sinatra's "My Way," told TMZ Monday he'd originally written "This Is It" for Jackson in 1983, recording a version of the song with the fallen pop star under the title "I Never Heard."

Anka told TMZ Jackson "stole the tapes" of the single from his studio -- and that he never got them back. The writer gave the song to a Latin-American pop artist, Safire, who released it in 1990 under the first title "I Never Heard."

He accused Jackson's camp of "ripping off my song" for Monday's release, then got in touch with Jackson's estate, who confirmed he had co-written the song.

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"We acknowledge that Michael and Paul wrote this song together," Jackson estate special administrator John Branca told TMZ.

Anka will receive 50 percent of the publishing rights from the single, TMZ reported.

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"I love the work that they've done on this new track, which I didn't do," Anka said.

The music legend also said Jackson executors said the song wasn't up to Michael Jackson's caliber -- and that it made sense Anka was behind its production.

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"'Now we know why the song was so good,''" Anka recalled co-special administator John McClain said.

But the co-writer behind the single didn't begrudge the Jackson estate once they gave him his rightful share.

"They did the right thing," Anka said. "I don't think that anybody tried to do the wrong thing. It was an honest mistake."

"This Is It," a slow ballad, was billed by producers behind the Sony movie "Michael Jackson's This Is IT" as an unreleased track found on a demo tape after the singer's death. Its lyrics and melody are almost identical to Safire's 1990 version.

Label reps did not respond to requests for comment.

Both Michael Jackson and Safire's versions of the song can be heard below.